Method of and means for electric welding



Oct. 27 1925.

A. E. PAIGE METHOD OF AND MEANS ROR- ELECTRIC WELDING Filed March 8, 1922 HGZ Zhmmtnr:

Patented Oct. 27, 1925.

UNITED STATES ARTHUR E. PAIGE, OF PHILADELPHIA, PENNSYLVANIA.

METHOD OF AND MEANS FOR ELECTRIC WELDING.

Application filed March 8, 1922.

To all whom it may concern Be it known that I. .hrrnru E. Pxmu, a citizen of the United States. residing at Philadelphia, in the county of Philadelphia and State of Pennsylvania. have invented a certain new and useful Improvement in Methods of and Means for Electric Welding.

My invention is particularly applicable to arc welding, by means of apparatus supplied from-a source of constant potential direct current.

Electric arcs are inherently unstable, because increase of current therein is accompanied by decrease of resistance and consumed voltage, and vice versa, decrease of current is accompanied by increase of resistance and voltage, and such inverse currentand voltage variations are cumulative, so that current will increase and voltage decrease until a short circuit of the source results, or current may decrease and resistance increase until the arc ruptures for lack of sustaining voltage. Consequently, it is impossible to supply such an are directly from a constant potential source. To overcome such inherent instability, a welding arc must be included in a circuit having a drooping volt-ampere characteristic, so that the tcndency to increase or decrease of current will he immediately compensated and checked by reduction or increase of voltage, respectively, thus maintaining constant wattage at the arc. Incidentally, it may he observed that the aforesaid properties of such an arc render impracticable the operation of two or more arcs in parallel in a single circuit.

In prior attempts to use a constant potential source of energy, for awelding are. the drooping volt-ampere characteristic aforesaid has been produced by including in the arc circuit a resistor which consumes voltage in proportion to current variations therethrough, thus leaving available for the arc, only the voltage difference between that of the supply and that consumed by such resistor. (onsequently, the etliciency of such apparatus is intolerablylow. because the energy expended in the resistor exceeds that available for the arc. For instance, theoretically. in a one hundred twenty volt system allording four k. w., at the arc, twenty k. W., are wasted in the resistor, leaving a current ctliciency of only sixteen and two-thirds per cent. However, the efficiency is in fact much less, because of the necessity for employing Serial No. 541,923.

current conversion apparatus. usually in the form of motor-gencrator sets. to develop the voltage required: for such a set further reduces the ag regate efliciency ol the entire apparatus. lor instance. an ordinary motorgenerator set for supplying a single arc with two hundred ampercs, flat compounded to maintain approximately titty volts in the arc circuit, has an efficiency of but sixty-live per cent.

'lheret'ore, it is an object and effect of my invention to provide apparatus capable of developing, in a welding are circuit, the desired volt-ampere characteristic aforesaid, without inclusion of such resistors or similar current regulating devices, and with the maximum attainable efiicicncy.

As hereinafter described, the principal element of my apparatus is a self-driven r0- tary converter. including but one rotor, and which afl ords a reduced short-circuit current at the instant of striking the are, and reduced voltage at the instant of breaking the arc, and is inherently capable of selfregulation to maintain the arc wattage substantially constant. Said rotor has conductors in slots spaced one hundred twenty degrees apart. forming a two path winding; with symmetrical end connections to a com nmtator, which commutator is provided with two main brushes which are diametri cally opposite and respectively positive and negative, and two negative brushes, extending radially, respectively in degrees angular relation with said main positive brush, upon-opposite sides thereof; said positive main brush being the positive terminal of the arc circuit and said two auxiliary brushes forming, together, the negative terminal of the are circuit. The field includes two diametrically opposite main poles, in line with said main brushes, and two auxiliary poles, respectively intermediate of said main oles, upon opposite sides of said rotor. The automatic regulation aforesaid is produced by the shifting of flux, causing an increasing flux in one main pole and a corresponding decreasing flux in the opposite main pole, in correspondence with fluctuations in the welding arc and corrective thereof. Incidentally, it may be observed that such construction and arrangement has an etliciency of upwards of sixtyfive per cent in apparatus affording a maximum of two hundred amperes, at twenty volts, effective at the arc, and affording a higher initial voltage to strike the arc; the welding current value being variable, by manually varying the exciting value of the auxiliary pole shunt windings, by means of a field rheostat, as hereinafter described.

My invention includes the various novel features of construction, arrangement and procedure hereinafter more definitely specified.

In the drawings;

Fig. I is a diagrammatic view indicating the wiring connections of a rotary converter, in cooperative relation with other elements of a convenient embodiment of my inven1 tion.

Fig. II is a diagrammatic elevation of the rotor of said converter and its field poles, indicated in Fig. I; indicating the magnetic flux in the same at open circuit.

Fig. III is a view similar to Fig. 11 but indicating the magnetic flux during welding operation of the apparatus.

Fig, IV is a diagram indicating the voltage around the commutator, by two annular lines, respectively corres onding with the open circuit condition 0 Fig. II and the closed circuit condition of Fig. III.

Said figures illustrate an embodiment of my invention particularly designed to use metallic electrodes from which metal, in fluid form, is transmitted through the arc to the work. It is characteristic of arcs through which metal is thus transmitted. that there is a rhythmic fluctuation in resistance thereof, at a rate of approximately twice per second, and of such character as is consistentwith the assumption that the metal is transmitted intermittently. Of course, it is impossible to either suppress or compensate the fluctuations in electrical energy in the welding circuit which are produced by such characteristic fluctuations at the welding arc. However, such a circuit manifests other fluctuations in energy coincident with fluctuations in resistance which are irregular and, as it were, superimposed upon the rhythmic fluctuations aforesaid.

I find that ifthe feeding motions of the article to be welded and the metallic electrode which is arranged to supply the fused metal thereto are effected at a uniform rate predetermined .in accordance with the quantity of fused metal it is desired to deposit per unit of length of the article; fluctuations in the electric energy of the circuit arising from fluctuations at the are are compensated automatically, for, when the resistance of the arc decreases, the amperage increases, causing the metallic electrode to fuse more rapidly, thus lengthening the arc gap and increasing the resistance of the arc, and, when the arc lengthens beyond the predetermined normal, thus increasin the resistance, the amperage is correspondingly decreased, so that said electrode is fused more slowly, and the are thus restored to its normal length and resistance.

It is generally assumed that such irregular fluctuations are due to variations in fusibility of the metal of the electrode aforesaid, and the prior art is replete with methods and means intended. to su press and compensate such fluctuations in tie voltage and amperage of arc welding circuits by modifying the predetermined normal condition of the circuit by mechanically or electrically operative means, or both. However, most of such compensatory means are too sluggish to have any efficiency for the purpose contemplated, but merely disturb the normal condition of the circuit and interfere with the inherently automatic self-regulation thereof above contemplated. On the contrary, my invention facilitates and supplements the aforesaid self-regulation of the arc.

Fig. I illustrates a convenient embodiment of my invention wherein 1 is the work to be welded and 2 a metallic electrode, arranged to form an electric welding are 3 as hereinafter described. Said work is arranged to be progressed by feeding mechanism exemplified by the feed wheel4which is operatively connected with the work, to progress it at a. uniform but adjustably variable rate. in the direction of the arrows marked thereon in Fig. I. Said electrode 2 is provided with feeding means, exemplified by the feed wheel 6 arranged to progress it at a uniform but adjustably variable rate, in the direction of the arrow marked thereon in Fig. I, and said feeding means are cooperatively connected, by any suitable means, which is preferably variable to vary the ratio of the respective feeding movements of said work and electrode. Such variable means may be respective trains of change gears, such as are ordinarily employed in a screw cutting lathe. However, the cooperative relation of said feeding mechanisms is exemplified in Fig. I by indicating said wheels 4 and 6 as in mesh with each other, and their connection, by any suitable means. with the driving element of the apparatus is exemplified in Fig. I by providing the axle T of said wheel 4 with the larger wheel 8, connected by the chain belt 9 with the driving wheel It) on the shaft 11 of the rotor 12 of the shunt wound motor variable voltage generator which is the principal element. in the conversion apparatus.

Said rotor 12, which is operatively connected to the feeding means for both the work 1 to be welded and the electrode 2 which is to supply the metal for the weld. through the are 3, at an adjustably predetermined and substantially uniform rate. as above contemplated, has conductors 14 located in slots pitched one hundred and twenty degrees apart upon the circumference of said rotor and connected to form an ordinary two path winding with symmetrical end connections to the sections'of the commutator 15.

The field for said rotor 12 includes the frame 16, which is preferably laminated and has two main poles l7 and 18, in diametrically opposite radial relation to the axis of said rotor 12, and two auiliary poles 20 and 21, in diametrically opposite radial relation to the axis of said rotor 12, and respectively intermediate of said main poles 1 and 18, upon respectively opposite sides of said axis. The positive main brush 23 and the negative main brush 24 are mounted in diametrically opposite sides of said commutator, in alinement with said main poles. The two auxiliary negative brushes 26 and 27 are respectively mounted in sixty degrees angular spaced relation with said positive main brush, upon opposite sides thereof. Said main brushes 23 and 24 are respectively connected to the positive and negative conductors 30 and 31 of a constant potential source of electric energy which is exemplified at 32 in Fig. I; although it is to be understood that said conductors 30 and 31 may be municipal supply lines extending from a remote generating station. However, it is to be understood that said conductors 30 and 31 afford current input to said rotor windings 14, whereby said rotor 12 is turned. Said main poles 17 and 18 are provided with respective field windings 33 and 34 which are connected in series with each other and in shunt relation with said rotor windings 14, whereby said main poles are oppositely polarized. Said auxiliary poles 20 and 21 are provided with respective field windi rs 36 and 37, in series relation with each ot ier and in shunt relation with said rotor windings 14, whereby said auxiliary poles are always polarized. alike, although their polarity is reversible as indicated by the letters N and S in Figs. II and III. The variable field rheostat, including the coils 39 and the movable contact 40, is included in the shunt circuit of said auxiliary pole windings and has the function and effect of determining the value of the welding current in accordance with the amount of resistance coil 39 included in said shunt field circuit.

Said auxiliary poles 20 and 21 also have respective field windings 42 and 43, which are respectively connected with said auxiliary negative brushes 26 and 27 and connected in common to the negative terminal ot' the welding arc. which terminal, in Fig. I, is the work 1. In this connection, it may be observed that I find it advantageous to constitute the metallic electrode 2, the positive terminal of the welding circuit for welding thin sheets with direct current, as such an arrangement effects fusion of said electrode at a faster rate than when the electrode is the negative terminal of such a circuit: because there is a greater concentration of thermal energy at the positive terminal and if the work, consisting of thin sheets of metal 1, were made the positive terminal, the concentration of thermal energy thereat might be such as to perforate such sheets. The welding circuit may be completed from said electrode 2, through the switch 44, directly to the positive conductor 30. However, for some classes of work, and particularly where the apparatus is intended for welding small articles 1 which are successively progressed with respect to the welding arc 3, so that it is necessary to frequentl start and stop such arc; I find it desira le to include, in series with the arc, an inductive resistance which checks the rush of current incident to striking the arc and acts as a reservoir of energy to maintain the arc. Such resistance is afforded by the coil 45, the effect of which is variable in accordance with the manually adjustable position of the contact 46. Moreover, I prefer to mount said coil 45 upon a laminated core 47 having a leakage gap 48 which may be varied in accordance with the position of the movable core member 50, which is adjustable by rotation of the screw 51.

The specific apparatus indicated in Fig. I is designed for connection with a direct current source of from one hundred to one hundred twenty-five volts constant potential, and is capable of converting the same to a maximum Welding current of two lumdred amperes at twenty volts. However, as above noted, the value of the welding current may be manually predetermined and varied by adjustment of the rheostat contact 40. Such adjustment is conveniently effected while the rotor 12 is running idly as a motor armature. For instance, as indicated by the annular line in Fig. 1V, such adjustment may be efl'ected to afford, in such open circuit, one hundred twenty volts potential across the main input brushes 23 and 24 and forty-five volts effective between the main positive brush 2; and the auxiliary negative brushes 26 and 27, which are located at equipotential points on the commutator. During such open circuit condition of the apparatus, the polarity of said auxiliary poles 20 and 21 and the consequent magnetic flux in the field and rotor are such as indicated by the letters and arrows in Fig. ll. However, upon closing the welding circuit, by permitting the electrode 2 to contact with the work 1, current will flow from said positive conductor 30 through the are 3, divide and pass through the two auxiliary opposing series field windings 42 and 43 and enter the rotor through the pair of negative brushes 26 and 27. Such change in the direction of the cur rent flow, alters the magnetic flux in the field and changes the polarity of said auxilmusk. M We iary poles. as indicated by the letters and arrows in Fig. III and, as indicated by the annular line 57 in Fig. IV, with one hundre'd twenty volts potential remaining across the main input brushes 23 and 24, the potential effective in the welding circuit, across from said brush 2.) to the auxiliary brushes 26 and 27, has fallen to twenty volts.

It may be observed with reference to Figs. II and III, that said auxiliary poles 20 and 21 are of like polarity under any condition, so that the converter combines the features of a two pole and a four pole structure, in that part of the armature conductors 14 are under the influence of the horizontal bipolar field, and part under the influence of a ninety degree field developed by one main pole and the two auxiliary poles.

When the are 3 is formed, as above described, approximately twenty-five per cent of the current in the welding circuit comes from the supply mains 30 and 31, such being the input current which drives the rotor 12. The remaining seventy-five per cent of the welding current is contributed by the generator action of the apparatus. The armature conductors 14 which contribute such current are marked in Fig. I with heavy crosses and dots and comprise onethird of the total number of said conductors 14. The other two-thirds of said rotor conductors 14, marked with the lighter crosses and dots, carry only the input current directly received from the constant potential supply conductors 30 and 31.

It may be observed that as two-thirds of the armature conductors 14. at any instant. carry only the input current, approximately twenty-five per cent of the total welding current and the other third of said conductors carry only the difference between the welding current and said input current, the resultant current value is such as to permit the use of conductors 14 of much smaller section than would be required in an ordinary generator of equivalent rating.

Such an are 3 as herein contemplated includes a central core of electrically charged particles with an envelop of hot gases, through which the metal from the electrode :3 passes in both vapor and liquid form; a spray of small globules being sometimes discernible in the arc stream. Atmospheric gases teml to ditt'use through such an arc stream and oxidize the incandescent metal in it. 'lherct'ore, it is desirable to maintain as short an arc 3 as possible, in order to minimize oxidation of the deposited metal, and the arc gap should not exceed oneeighth of an inch in length and, advantageously, may be much shorter. An arc voltage of twenty-five indicates an arc gap of approximately one-eighth of an inch length. Consequently, it is advantageous to maintain the welding are potential at not more than twenty volts, as above indicated, and preferably not more than sixteen.

The maintenance of the are by the stabilizing characteristics of the electric elements aforesaid is facilitated by affording stabilizing characteristics in the are gases. Therefore, I prefer to employ for an electrode 2, commercially pure iron, alloyed with 0.18 per cent carbon and 0.05 per cent manganese; for the combination of atmospheric oxygen with the manganese and carbon liberated from such an electrode forms a mixture of manganese oxide vapor and carbon dioxide gas at the are which re stricts further diffusion of atmospheric gases into the are stream.

If the flow of fused metal from the electrode 2 is too slow, it causes excessive penetration of the article being welded. If too fast, it produces excessive overlap, i. e., the deposited metal overlaps the work without adhering to it. Therefore. it is important to note that the electrode 2 should be of such diameter that the current density is approximately eight thousand amperes per square inch; which equals one thousand two hundred and forty amperes per square centimeter. That means sixty amperes for an electrode three-thirty-seconds of an inch in diameter; one hundred amperes for an electrode one-eight of an inch in diameter; one hundred and fifty-five amperes for an electrode five-thirty-seconds of an inch in diameter; and two hundred and twenty-five amperes for an electrode three-sixteenths of an inch in diameter. Moreover. the electrode 2 should be less fusible than the work 1. i. e., it should have a higher melting point, so as to insure that the work is maintained at such temperature that the metal falling upon it from the electrode 2 shall coalesce therewith.

Incidentally. it may be observed that the depth of the arc crater of fusion in the work, exemplified at 1, in Fi I, should be approximately one-sixteenth of an inch. unless the work is of less thickness which it is desirable to avoid penetrating.

The articles 1, indicated in Fig. I, are split. cylindrical blanks for ice-cream cans, which are successively longitudinally progressed. with their split edges passing through said are 3, in the direction of the arrows marked thereon. by endless chains (30 carried by sprocket wheels 61 mounted on shafts 62 and 63 in the frame (it. Said frame (54 is suspended by the central web hanger 65 which extends through the split portions of said tubes. Said chains 60 are progressed hy means of the worm gear 67 on the shaft 62: which gear is turned by the worm 69, carried by the vertical shaft 70. Said shaft 70 has, at its upper end, the bevel gear 72 engaging the bevel gear 73 on the shaft 74; which latter has, at its rear end, the bevel gear 76 engaging the bevel gear 77 on said shaft 7 However, such welding apparatus is claimed in another application for Letters Patent of the United States, copending herewith.

Although I have found it convenient to illustrate my invention with reference to apparatus capable of employing metallic electrodes to supply the metal which is transmitted through the are; it is to be understood that I do not desire to limit myself to the employment of such electrodes, as my invention may be :ulvantageously employed in apparatus wherein the electrodes are of carbon or graphite or other non-metallic compositions.

I do not desire to limit myself to the. precise details of construction or arrangement or method of operation of my invention as herein set forth, as it is obvious that various modifications may be made therein, without departing from the essential features of my invention, as defined in the appended claims.

I claim:

1. In electric arc welding apparatus; the combination with feeding means arranged to feed the work and a metallic electrode to ward each other, at a uniform predeterminable rate; of a single rotor arranged to drive said feeding means; said rotor having a circumferential series of conductors; means supplying constant potential direct current to a circlunferentially limited motor sector of said series of rotor conductors, to rotate said rotor; means constituting the remaining circumferential sector of said series of rotor conductors, a generator sector, in the same circumferential zone with said motor sector; a field for said rotor, including two main poles and two auxiliary inter-poles; a shunt field winding on each of said poles; opposed series windings on said interpoles; a welding arc circuit, including said work, electrode, series field windings, and rotor; and an adjustable field rheostat in the shunt circuit, including said shunt field windings; said rheostat being adjustable to vary the energy in said are circuit; and said rotor and its field being automatically operative to regulate the energy in said are circuit and compensate for fluctuations in resistance at; the are.

2. In electric arc welding apparatus; the combination with feeding means arranged to feed the work and a metallic electrode toward each other, at a uniform predetermined rate; of a single rotor arranged to drive said feeding means: said rotor having a circumferential series of conductors; means supplying consl ant potential direct current to a circumfercntially limited motor sector of said series of rotor conductors, to rotate said rotor; means constituting the remaining circmnferential sector of said series of rotor conductors, a generator sector, in the same circumferential zone with said motor sector: a field for said rotor, including main poles and auxiliary interpoles; a shunt field winding on each of said oles opposed series windings on said inter-p0 es; a Welding arc circuit, including said work, electrode, series field windings, and rotor and a resistancev in circuit with said shunt field windings and adjustable to vary the energy in said are circuit: and said rotor and its field being automatically operative to regulate the energy in said are circuit and compensate for fluctuations in resistance at the arc.

3. in electric arc welding apparatus; the combination with feeding means arranged to feed the work and a metallic electrode toward each other, at a variable rate; of a single rotor arranged to drive said feeding means; said rotor having a circumferential series of conductors; means sup 'ilying constant potential direct current to a circumferentially limited motor sector of said series of rotor conductors, to rotate said rotor; means constituting the remaining circumferential sector of said series of rotor conductors a generator sector, in the same circumferential zone with said motor sector; a field for said rotor, including main poles and auxiliary inienpoles; a shunt field winding on each of said poles: opposed series wind ings on said intcrpoles; a welding arc circuit, including said work, electrode. series field windings, and rotor; and a resistance in circuit with said shunt field windings, and adjustable to vary the energy in said are circuit; and said rotor and its field being automatically operative to regulate the energy in said are circuit and compensate for fluctuations in resistance at the arc.

4. in electric arc welding apparatus; the combination with f eding means arranged to feed the work and a metallic electrode toward each other; of a single rotor arranged to drive said feeding means: said rotor having a circnml'crential scries of conductors; means supplying constant potentiai direct current to a circumfcrentially limited motor sector of said series of rotor conductors, to rotate said rotor; means constituting the remainiug circlllnfcrcnl ial sector of said series of rotor conductors, a generator sector, in the same circumfcrcntial zone with said inotor sector; a field for said rotor, including main poles and auxiliary inter-poles; a shunt field winding on each of said poles; opposed series windings on said inter-poles: a welding arc circuit, imluding said work, electrode. series field windings, and rotor; and a resistance in circuit with said shunt field windings, and :aljustablc to vary the energy in said arc circuit; and said rotor and its field being automatically operative to regulate the energy in said are circuit and compensate for fluctuations in resistance at the are.

5. In electric arc welding apparatus; the

combination with feeding means arranged to feed the work and an electrode toward each other; of a single rotor arranged to drive said feeding means; means supplying constant potential direct current to a circumferentially limited motor sector of said rotor, to rotate said rotor; means constituting the remaining circumferential sector of said rotor. a generator sector, in the same circumferential zone with said motor sector; a field for said rotor, including main poles and auxiliary inter-poles; a shunt field winding on each of said poles; opposed series windings on said inter-poles; a welding are circuit, including said work, electrode, series field windings, and rotor; said rotor and its field being automatically operative to regulate the energy in said arc circuit and compensate for fluctuations in resistance at the are.

6. In electric arc welding apparatus; the combination with feeding means arranged to feed the work and an electrode toward each other; of a single rotor arranged to drive said feeding means; means supplying constant potential direct current to a motor sector of said rotor to rotate said rotor; means constituting another sector of said rotor, a generator sector, in the same circumferential zone with said motor sector; a field for said rotor, including main poles and auxiliary inter-poles; a shunt field winding on each of said poles; opposed series windings on said inter-poles; a welding arc circuit, including said work, elec trode, series field windings, and rotor; said rotor and its field being automatically operative to regulate the energy in said are circuit and compensate for fluctuations in resistance at the are.

7. In electric arc welding apparatus; the combination with feeding means arranged to feed the work and an electrode toward each other at a predeterminable rate; of a single rotor arranged to drive said feeding means; means arranged to supply current from an exterior source, to a motor sector of said rotor, to rotate said rotor; means constituting another sector of said rotor a generator sector, in the same circumferential zone with said motor sector: a field for said rotor; a welding arc circuit, including said work. electrode, windings of said field. and rotor: said rotor and its tield being antomatically operative to regulate the energy in said arc circuit and compensate for tluctuations in resistance at the arc.

8. The method of electric arc welding. which consists in feeding the work to be welded and an electrode in cooperative relation with each other at a uniform rate, by a single rotor which is rotated by current input from a constant potential source; said rotor being rotated in a tield including two main poles which are of opposite polarity,

and two intermediate poles which are always of like polarity but of automatically reversible polarity; affording a reduced short-circuit current at the instant of striking the arc and reduced voltage at the instant of breaking the are; and automatically regulating the arc wattage by causing finctuations in the arc to produce counter-effects in the shifting of magnetic flux in said rotor and field, manifested by an increased flux in one main pole and a corresponding decreased flux in the opposite main pole, in correspondence with such fluctuations in the arc and corrective thereof.

9. The method of electric arc welding, which consists in feeding the work to be welded and an electrode in cooperative relation with each other at a predetermined ratio, by a single rotor which is rotated by current input from a constant potential source; said rotor being rotated in a field including main poles which are of opposite polarity, and intermediate poles which are always of like polarity, but of automatically reversible polarity; att'ording reduced shortcircuit current at the instant of striking the arc and reduced voltage at the instant of breaking the arc; and automatically regulating the arc wattage by causing fluctuations in the arc to produce counter-effects in the shifting of magnetic flux in said rotor and field, manifested by an increased flux in one main pole and a corresponding decreased flux in the opposite main pole, in correspondence with such fluctuations in the arc and corrective thereof.

10. The method of electric arc welding which consists in feeding the work to be welded and an electrode in cooperative relation with each other, by a rotor which is rotated by energy from an exterior source: said rotor being rotated in a field including main poles which are of opposite polarity. and auxiliary poles which are always of like polarity but of automatically reversible polarity; and automatically regulating the arc wattage by causing fluctuations in the arc to produce counter-effects in the shifting of magnetic flux in said rotor and field.

11. The method of electric arc welding which consists in feeding the work to be welded and an electrode in cooperative relation with each other, by a rotor, which is rotated by current input from an exterior source; said rotor being rotated in a lield including main poles which are of opposite polarity, and auxiliary poles which are always of like polarity but of automatically reversible po|arit including windings of said rotor and windings of its lield in the arc circuit; and automatically regulating the are by causing fluctuations in the arc to produce counter-cfl'ects in the shifting of magnetic tlux in said field.

"Ill

12. In electric arc welding apparatus; the combination with feeding means arranged to feed the work and an electrode in coordinated relation; of a motor generator. including a rotor and a field, arranged to drive said feeding means; said rotor and field being automatically operative to regulate energy in said are circuit and compensate for fluctuations in resistance at the are, by means of a commutator provided with four brushes: three of said brushes being equally spaced one hundred and twenty degrees apart, in a circumferential series, and the .fourth brush being interposed between two of said equally spaced brushes; said interposed brush being connected to the positive terminal of the welding are.

13. In electric arc welding apparatus; the

combination with feeding means arranged to feed the work and an electrode in coordinated relation; of a motor generator, in cluding a rotor and a field, arranged to drive said feeding means; said rotor and field being automatically operative to regu late energy in said are circuit and compeir sate for fluctuations in resistance at the arc, by means of a commutator provided with four brushes; three of said brushes being equally spaced one hundred and twenty degrees apart, in a circumferential series and the fourth brush being interposed between two of said equally spaced brushes.

In testimony whereof, I have hereunto signed my name at Philadelphia, Pennsyl- Vania, this third day of March, 1922.

ARTHUR E. PAIGE. 

